If you delete every newbie's bad work, they'll think that they shouldn't try.
Any site member's work is subject to the same rating system, regardless of whether said user is a newbie or a veteran. More information on the deletions process is here: https://scp-wiki.wikidot.com/deletions-guide
Writing for the SCP wiki is not easy, as the site has been around for more than a decade and there are already thousands of articles in the mainlist. It is up to the author to determine how motivated they are to revise and resubmit their work if a piece of theirs reaches deletion threshold. If an author would like to post material for reading without voting, they may submit to the Fan Work forum: https://scp-wiki.wikidot.com/forum/c-662937/fan-work
You do give feedback. But it doesn't say how to improve. You just say "this sucks. here's why."
As noted in the writing guides, the mainsite is for summary judgment. No readers are obligated to give a response beyond than their vote—more in-depth review is expected to occur before something is posted for voting. This can be done in the mainsite forums (https://scp-wiki.wikidot.com/forum/c-89000/help:ideas-critique / https://scp-wiki.wikidot.com/forum/c-50864/help:drafts-critique), IRC, Discord, private Wikidot messages, and so on.
Of note, most reviewers are hesitant to provide detailed feedback if there isn't a clear indication that an author will respond well to critique. Additionally, the pool of hopeful authors vastly outnumbers the population of experienced reviewers who are able and willing to provide quality feedback. Furthermore, all reviewers on the site are unpaid volunteers providing favors in their free time, and they don't receive any authorship credit for the material they assist with. Because of this, first impressions tend to be important when a reviewer determines whether they will spend the time to comment on someone's work or not.
In the case of an author finding critique unhelpful, their response to the reviewer(s) will affect the likelihood they will receive further assistance from other readers. The best thing to do in those situations would be to ask for clarification, or simply thank the reviewer for their time and politely move on. If a reviewer is being rude or breaks rules, the author should cease responding to them and notify a staff member of the behavior.
Second, I'm going to be burning until you put me out. At this rate, it won't happen. And for the record, the timing you guys decided to delete SCP-7956 couldn't have been worse. I'm usually pretty calm, but someone had managed to really piss me off. sorry for the outburst.
It's good that you acknowledge the outburst being atypical. I hope that that whatever circumstance led to it improves.
But the question is genuine: why was I there if nobody wanted me there? I'm waiting for the answer.
I don't think I can answer your question; I don't know why you joined the site or why you chose to stay for the length of time you did.
I believe it might be worthwhile to take the time to interact with the community before posting more of your work, so you feel like part of the site as an individual with a shared interest rather than someone no one wants around. Discuss the lore and worldbuilding in the forums and article threads, maybe read through some critique conversations, start remembering some names so you can start seeing other people as peers. Find people to work with so you aren't overly reliant on just yourself or one or two other site members.